strip string routine

Author: jacobwilliams

src/string_module.f90

@@ -16,6 +16,7 @@ module string_module
     public :: replace_char
     public :: reverse
     public :: lchop, rchop
+    public :: strip
 
     contains
 !*****************************************************************************************
@@ -152,6 +153,60 @@ pure function reverse(str) result(newstr)
     end function reverse
 !*****************************************************************************************
 
+!*****************************************************************************************
+!>
+!  Strip all occurances of chars from the beginning and end of the string.
+
+    pure function strip(str, chars) result(newstr)
+
+    character(len=*),intent(in) :: str  !! original string
+    character(len=*),intent(in),optional :: chars !! characters to strip
+    character(len=:),allocatable :: newstr !! new string
+
+    integer :: i !! counter
+    integer :: n !! length of str
+    integer :: idx !! for using scan
+    integer :: start_idx, end_idx  !! substring to keep
+
+    if (present(chars)) then
+        if (chars /= '') then
+            ! have to step through manually from beginning and end
+            n = len(str)
+            start_idx = 1
+            end_idx = n
+            ! forward search
+            do i = 1, n
+                idx = scan(str(i:i), chars)
+                if (idx > 0) then
+                    start_idx = start_idx + 1
+                else
+                    exit
+                end if
+            end do
+            ! backward search
+            do i = n, 1, -1
+                idx = scan(str(i:i), chars)
+                if (idx > 0) then
+                    end_idx = end_idx - 1
+                else
+                    exit
+                end if
+            end do
+            if (end_idx <= start_idx) then
+                newstr = ''  ! all stripped
+            else
+                newstr = str(start_idx:end_idx)  ! return substring
+            end if
+            return ! done
+        end if
+    end if
+
+    ! in this case assuming it's a space, so use intrinsic functions
+    newstr = trim(adjustl(str))
+
+    end function strip
+!*****************************************************************************************
+
 !*****************************************************************************************
     end module string_module
 !*****************************************************************************************

test/string_test.f90

@@ -30,5 +30,20 @@ program string_test
     s1 = rchop('abc efg', 'efg')
     if (s1 /= 'abc' .and. s1(4:4) /= ' ') error stop 'rchop test failed: '//s1
 
+    s1 = strip('   hello world   ')
+    if (s1 /= 'hello world' .and. len_trim(s1)/=11) error stop 'strip test failed: '//s1
+
+    s1 = strip('xxxxhelloxworldxxxx', 'x')
+    if (s1 /= 'hello world' .and. len_trim(s1)/=11) error stop 'strip test failed: '//s1
+
+    s1 = strip('abchelloxworldcccccab', 'bac')
+    if (s1 /= 'hello world' .and. len_trim(s1)/=11) error stop 'strip test failed: '//s1
+
+    s1 = strip('abchelloxworldcccccab ', 'bac')
+    if (s1 /= 'hello worldcccccab ' .and. len(s1)/=19) error stop 'strip test failed: '//s1
+
+    s1 = strip('abcaaabbbcccaaa', 'bac')
+    if (s1 /= '' .and. len(s1)/=0) error stop 'strip test failed: '//s1
+
     end program string_test
 !*****************************************************************************************